In general, inkjet printing machines or printers include at least one printhead unit that ejects drops of liquid ink onto recording media or an imaging member for later transfer to media. Different types of ink may be used in inkjet printers. In one type of inkjet printer, phase change inks are used. Phase change inks remain in the solid phase at ambient temperature, but transition to a liquid phase at an elevated temperature. The printhead unit ejects molten ink supplied to the unit onto media or an imaging member. Once the ejected ink is on media, the ink droplets quickly solidify.
The media used in both direct and offset printers may be in sheet or web form. A media sheet printer typically includes a supply drawer that houses a stack of media sheets. A feeder removes a sheet of media from the supply and directs the sheet along a feed path past a printhead so the printhead ejects ink directly onto the sheet. In offset sheet printers, a media sheet travels along the feed path to a nip formed between the rotating imaging member and a transfix roller. The pressure and heat in the nip transfer the ink image from the imaging member to the media. In a web printer, a continuous supply of media, typically provided in a media roll, is entrained onto rollers that are driven by motors. The motors and rollers pull the web from the supply roll through the printer to a take-up roll. As the media web passes through a print zone opposite the printhead or heads of the printer, the printheads eject ink onto the web. Along the feed path, tension bars or other rollers remove slack from the web so the web remains taut without breaking.
Regardless of the type of media used, media heating helps transfer the ink more efficiently to the recording media. In web-fed printers, media heaters typically comprise one or more radiant heaters that are positioned along the media pathway. These heaters raise the temperature of the moving web. Adjusting the power supplied to the heaters controls the output of the radiant heaters. The printing system typically includes a thermal sensor positioned adjacent the media pathway to detect the temperature of the moving web and provide the detected temperatures to a controller. The controller may compare the detected temperatures to temperature thresholds to adjust the power provided to the heaters to maintain the temperature of the media web in appropriate temperature ranges at different locations along the feed path.
Existing radiant heaters used in printers generate heat using high-temperature lamps with one typical lamp having a filament configured to heat to 1200° C. with a surface temperature of 800° C. In operation, these lamps emit radiant energy with a range of wavelengths including portions of the visible spectrum at approximately 0.7 μm through portions of the infrared spectrum at 1.5 μm to 2.5 μm. Some of these lamps are relatively energy inefficient, and require separate reflector elements to redirect radiant energy toward the print media to bring the print media to an appropriate temperature. The energy consumption of the radiant heaters is one factor affecting the operating cost of the printing device. Thus, improvements to radiant heaters that can heat print media while reducing the power usage of printing devices are desirable.